|Budget Amount *help
¥2,500,000 (Direct Cost : ¥2,500,000)
Fiscal Year 1998 : ¥100,000 (Direct Cost : ¥100,000)
Fiscal Year 1997 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1996 : ¥2,100,000 (Direct Cost : ¥2,100,000)
This paper proposes a magnetic measurement principle to develop a balance sensor. Basically, the sensor is composed of a spherical vessel sealing certain amount of liquid, a mushroom-shaped float and a permanent magnet. The circular plated magnet is fixed on the root of the float stem. According as the liquid moves in the vessel, the float changes the position of the magnet. And the Hall effect devices located around the vessel sense the change of balance with the aid of a signal processor.
At first, the density of the Hall effect devices and the algorithm for determining the direction of the resultant acceleration are considered. Also, the results of experiments for magnet's position and the angle of balance are shown. Then, the measurement error is analized since the magnet is free to move on the float in the vessel and the measurement error is caused not only by the position eror of the Hall-Effect device located at the vessel exterior, but also by the clearance betweeen the float an
d the vessel interior. In particular, the errors produced by the changes of the float's height, position on the liquid surface. and inclination are investigated and calculated by supposing possible changes of the sensor parameters in the practical application.
Finally, we extend the measurement principle so that we can sense not only the direction of acceleration but also the azimus in 3-D space. Basically, the sensor is composed of a spherical vessel filling a considerable amount of liquid, a mushroom-shaped float moving freely with a small clearance in the vessel, two permanent magnets fixed at the float's cap and stem, and Hall-effect devices located around the vessel exterior. We describe the structural mechanism of the sensor head and investigate the mathematical formulation to estimate the magnetic flux intensity sensed by the Hall devices, and also the signal processing algorithm for determining the magnet position as a common point of magnetic potential curves depicted by using the Hall output. The data of magnetic flux intensity obtained by calculation and experiment are compared to verify the validity of the measurement principle. The proposed method is effective in detecting all directions of the resultant acceleration of motion and gravity with uniform resolution, since the sensor has no rotation axes. Less